1. Field of the Invention
The present invention relates to a write current setting method, and a recording and reproducing device. In particular, the present invention relates to a write current setting method, and a recording and reproducing device, in which the optimum write current of the device is set, the device recording information on a recording medium in accordance with the write current.
Recently, in a hard disk drive device, high-density recording and high-speed recording and reproducing have been performed. As high-density recording and high-speed recording and reproducing have been performed, optimizing of a recording current has been demanded. The recording current varies depending on the temperature.
In order to optimize the write current, it is necessary to set the write current so that maximum margins can be obtained in a low temperature condition and in a high temperature condition, respectively.
2. Description of the Related Art
FIG. 1 shows a plan view of one example of a magnetic disk device in the related art. In a magnetic disk device 11 shown in FIG. 1, an actuator 12 is provided with arms 13. A supporting spring mechanism 13a is provided to the extending end of each arm 13. Each arm 13 is provided with a magnetic head 14 at the extending end thereof. A base portion of the arms 13 is rotatably supported by a pivot 15. The arms 13 are positioned between adjacent ones of a plurality of magnetic disks 20 which will be described later.
A coil supporting portion 16 is provided at the side opposite to the arm 13 with respect to the pivot 15. A coil 17 is wound on the coil supporting portion 16. Two magnets 18a and 18b are fixed below the coil 17. The coil 17 and magnets 18a, 18b form a VCM (Voice Coil Motor).
In the magnetic disk device 11, the plurality of magnetic disks 20 are fixed to a spindle motor and are rotated by the spindle motor. The arm 13 is rotated as a result of a current being supplied to the coil 17 from a wiring board 21 via a flexible printed board 22. Thereby, with respect to these magnetic disks 20, the arms 13 are rotated so that each magnetic head 14 moves in a radial direction of the magnetic disks 20.
As each magnetic head 14, a thin-film head is used, and the magnetic heads 14 float by a predetermined amount due to the rotation of the magnetic disks 20, respectively. Each thin-film magnetic head 14 includes a write head formed as a result of forming a coil and a magnetic gap in a thin-film formation technique, and is formed on a slider. Each thin-film magnetic head 14 further includes a read head using a magneto-resistive device and is also formed on the slider. A predetermined current (write current) is supplied to the coil of the write head. Thereby, writing data to the respective magnetic disk 20 is performed through leakage magnetic flux occurring from converting electricity to magnetic flux. The data written on the magnetic disk is read through the read head and a waveform corresponding to the write current (amplitude of a read current) is obtained.
FIGS. 2A and 2B show graphs of a relationship between the write current and head characteristics. FIG. 2A shows the characteristics of the write current with respect to head output levels. FIG. 2B shows the characteristics of the write current with respect to overwrite gains. Generally speaking, the write current is determined from the saturation characteristics of the output levels of the magnetic head 14 (FIG. 2A) and the overwrite gains (FIG. 2B).
In the related art, the write current is determined from measuring the crosstalk characteristics between the heads and media and overwrite characteristics. From the determined write current, the resistance inside each magnetic disk is determined. Thus, the write current is fixed.
Further, the magnetic disks are affected by the temperature. Thereby, the optimum write current changes. Therefore, setting of the write current should be performed in consideration of the temperature variation.
Japanese Laid-Open Patent Application Nos. 63-167404, 1-245406 and 1-317208 proposed methods for setting the write current in accordance with the temperature.
In these arts, a temperature sensor and a table in which the optimum write currents are set for particular temperatures are provided inside a magnetic disk device. Thereby, the write current is controlled in accordance with the detected temperature of the temperature sensor. Thus, information can be written in a disk independent of the temperature. In these arts, the overwrite characteristics are measured and the optimum write currents are set.
However, in the related art, the crosstalk characteristics between heads and media and the overwrite characteristics are measured and the write current of a magnetic disk drive is determined. Accordingly, these measurements are difficult after these components are built in and circuits are connected therewith. If the measurements can be performed, the measurements require a long time.
In these arts of Japanese Laid-Open Patent Application Nos. 63-167404, 1-215406 and 1-317208, it is necessary to provide the temperature sensor and a memory in the magnetic disk device. Accordingly, the costs of the device are high. Further, in these arts, because the overwrite characteristics are used, a long time is required for setting the optimum write currents.